I hope I'm wrong, but if ZCash delivers on the technical promise the blowback from legislators and law enforcement is sure to result in a net loss of privacy for everyone. Enabling illegal profiteering from the very real pain and suffering of others almost always results in government actio (appropriately so); but also legislative over-reaching (eg. mandated sentencing legislations, zero tolerance policies, warrantless wiretapping) because ZCash's message of economic and societal benefits will be utterly lost amid stories of how the tech hurt people.
ZCash is very impressive. Brilliant even. But for those who want better privacy... elect leaders who share the concern. Donate to the EFF and ACLU. Advocate for a 'privacy czar' as a cabinet/ministerial level position.
The same could be said of strong encryption: if people use it, the government might crack down.
On the other hand, the more people use encryption, the less useful mass surveillance will be to the government. When the government no longer gets much worthwhile information from eavesdropping, it may be easier to get politicians to put a halt to eavesdropping.
So it could be that the best way to protect privacy is to use both technical and political approaches.
I think many prefer non-violent direct action, for good reason. The cost to the government to spy on you is so low, cryptographically enforcing privacy is the only way to guarantee it.
If successful ZCash cryptographically guarantees more government regulation and surveillance to counter the very real and also the very irrational fears of harm anonymous payments make possible. It will have opposite the desired impact on privacy if it takes off. I want to be wrong about this, but experience tells me otherwise.
ZCash is very impressive. Brilliant even. But for those who want better privacy... elect leaders who share the concern. Donate to the EFF and ACLU. Advocate for a 'privacy czar' as a cabinet/ministerial level position.